This invention relates to a composition of thermoplastic elastomeric triblock polymer particles in a soft polyurethane matrix.
Elastomeric polymer compositions have a variety of uses. Very soft elastomeric polymers are of more restricted use but serve in a number of vital applications. Film and slabs of very soft elastomeric polymers are useful in certain cushioning applications, such as packaging of delicate parts, anti-vibration cushioning, and especially in prosthesis applications such as cushioning artificial limbs and other devices.
However, most elastomer compositions are formulated in a single phase and must have carefully tailored properties for any specific particular application. Also, single phase soft compositions tend to "bottom out" in use. That is, because of the softness--which can be as soft as the consistency of gelatin--the elastomer will move or flow from under a pressure point, leaving the pressure point unsupported and without cushioning. This can be a serious problem in some applications--leaving a delicate body part without adequate protection or a cushioned limb exposed to injury.
Triblock copolymer elastomers, such as the KRATON.RTM. elastomers from Shell Chemical Company, can be oil or plasticizer extended to obtain very soft compositions. However, they are single phase and when they contain excess oil they tend to "bleed". Very soft compositions of polyurethanes can be obtained, but they also tend to "bottom out" in use.
The present invention is a composite composition that will not "bottom out" and a method of making the composition.